RATIONALE: Monoclonal antibodies, such as rituximab, can block cancer growth in different ways. Some block the ability of cancer cells to grow and spread. Others find cancer cells and help kill them or carry cancer-killing substances to them. Bortezomib may stop the growth of cancer cells by blocking some of the enzymes needed for cell growth and by blocking blood flow to the tumor. Drugs used in chemotherapy, such as doxorubicin, dexamethasone, and chlorambucil, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Giving combination chemotherapy together with rituximab and bortezomib may kill more cancer cells.